SYDNEY, Aug 9 (Reuters) - Australian casino giant Crown Resorts Ltd filed a lawsuit on Friday to protect its views of Sydney Harbour from a neighbouring development backed by two of the country's richest families and a Chinese billionaire.

The suit against the state government sets the scene for a fight over one of Sydney's most prized possessions, harbour views, between the casino company of billionaire James Packer and a group of powerful adversaries who took over the six-hectare (15-acre) former stevedoring site next door in January.

They are mall giant Westfield Corp founder Frank Lowy, Australia's biggest privately-held construction firm Grocon Pty Ltd, which has been owned by the same family since it was founded in 1948, and residential developer Aqualand, owned by Chinese property investor Yi Lin.

In an earnings update on Thursday, Crown said was seeking a court order forcing the government of New South Wales to negotiate any changes to planning rules which currently "ensure that sight lines from the Harbour Bridge to the Sydney Opera House are retained for the Crown Sydney Hotel Resort".

The statement did not elaborate and Crown's lawyer declined to comment. However the state government, which has been planning to sell the harbourside stretch of land known as Barangaroo to developers since 2012, recently increased the floor-size limit on the neighbouring block.

A spokesman for the government's Barangaroo Delivery Authority said it had been negotiating with Crown about sightlines for 28 months.

"The authority will defend its position in court," he added.

Representatives for Lowy's Australian company, Scentre Group , and Aqualand were not immediately available for comment, while Grocon declined comment.

Barangaroo is the last major development site on Sydney Harbour and the casino development has been controversial from the start, with the government accused of selling prime public space to a billionaire with a business aimed at high-roller Chinese gamblers.

The government has sought win over a sceptical public by guaranteeing waterfront public space in the precinct and building a train station under the development next to Crown.

Packer, who quit the Crown board earlier this year citing mental illness, bought two residential floors at his Barangaroo resort for A$60 million last year, setting a new record apartment price for the city.